Grid with custom rows and query

Important. This is a complex example. Before reading it, please study allgrid and all previousquery examples.

Also complex grids that list different item types in edit mode may use query facilities.
However, some cautions must be taken. Namely:

All item types have a custom ancesctor, called main item ViewModel whose rendering is usually defined in the first RowType.
Query, behavior is defined in the main item ViewModel, since all query may involve just properties common to all item types.

In the repository together with the instruction that specifies how to project db data in
the various item ViewModels :